An online voiced skit released to promote Tales of the Heroes: Twin Brave reveals that the next boss for the game may be Duke from Tales of Vesperia.UPDATE (Feb 03, 2012): A leaked magazine scan has officially confirmed Duke, showing his new status art and Mystic Arte cut-in. It's also confirmed that the boss characters are playable, though it has not been confirmed yet whether they will be having their own paths in Story Mode or if they will only be available via the game's Free Mode:
In the skit, we have Asbel Lhant (Tales of Graces) and Milla Maxwell (Tales of Xillia) introducing their "enemies", with Duke being in this skit, which I can only assume to be the same Duke from Tales of Vesperia. Milla mentions that this Duke, despite being an enemy, seems to be an impressive man who seems to hold strong his wishes and does not waste time acting on what he must act on. However, what he's doing seems to be detrimental to the people Asbel wants to protect.
It is further discussed that the Duke in this game wants to use the Eternal Sword to change something in the past. Whatever this past may be, Milla comments that it would be the reason why Duke is acting as such.
Also, fun fact, since I believe it was never mentioned in-game. Duke's last name is Pantarei. It was only mentioned in some of the game's Japanese guides.
Tales of the Heroes: Twin Brave will be out for the PSP in Japan on February 23, 2012. Play-Asia now has pre-orders open for both the regular version and the premium box. The first demo is also now available either from the PlayStation Network or the game's official site.